A known method of attaching a semiconductor integrated circuit device to a printed circuit board or other substrate is to use a flip chip attachment. Integrated circuit devices configured for flip chip attachment typically have a first surface which has a plurality of conductive bonding pads at its periphery. Bumps of metallic solder are formed on the bonding pads. The device is mounted with its first surface facing the substrate. The solder bumps are subsequently reflowed so that conductive metal-to-metal bonds are formed with mirror-image conductive metallizations on the circuit board or other substrate. Additional background information on flip chip attachment may be found in U.S. Pat. No. 5,478,007.
The use of a flip chip attachment between an integrated circuit device and a substrate has advantages, such as eliminating the need for bond wires and improving the electrical conduction between the between the integrated circuit device and the external metallization on the substrate.
Conventionally, certain types of integrated circuit devices are not mounted on substrates using a flip chip attachment. Such devices include charge coupled devices ("CCD"), erasable programmable read only memory ("EPROM") devices, and other light sensitive integrated circuit devices, such as those used in cameras, fingerprint recognition equipment, and scanners. These types of integrated circuit devices require a selected or continuous transmission of light onto a surface of the integrated circuit where light sensitive circuitry is located. Conventionally, this requirement precludes a flip chip attachment, because the light sensitive circuitry is typically on the same surface of the device as the bonding pads and the solder bumps. The light sensitive circuitry would face the substrate if a flip chip attachment were used, and thus light would not be directly incident on the light sensitive circuitry.
A mounting for connecting CCD, EPROM, or other optical integrated devices using a flip chip attachment would have wide application, because of the electrical advantages of lower capacitance, inductance, and resistance typically associated with a flip chip attachment.